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Animal antics Penguins can sniff out the odour of lifelong mates, helping them reunite in crowded colonies, a new study has found.

The birds' highly attuned sense of smell also allows them to identify the scent of close kin to avoid inbreeding, say the researchers from the University of Chicago.

Some seabirds have previously been known to use their sense of smell to find food or locate nesting sites, but this is the first study to show how penguins use scent to discriminate between close relatives and strangers, they report in the journal PLoS ONE.

"Other animals do it, we do it, so why can't birds?" asks Jill Mateo, who worked on the research led by graduate student Heather Coffin.

"Their sense of smell can help them find their mates and perhaps choose their mates," says Mateo.

"Seafaring birds that travel long distances in the ocean use odours to find food and use odours to recognise nests, but we didn't know what odours or the extent to which they could use odours to recognise kin."

The birds' behaviour was recorded as they examined scents emitted by oil from their preening glands. The gland near the bird's tail excretes oil used to keep them clean but also has an olfactory purpose.

In one experiment, penguins with mates preferred the comfort of their mates' scent over the scents of unfamiliar penguins. In another, penguins without mates spent twice as long investigating unfamiliar penguins' scents than those belonging to their close relatives.

"In all sorts of animals that we study, including human babies, novel odours, novel cues, are investigated longer than less-novel cues," says Mateo.

She says scent is used by many species to attract mates, or to avoid mating with relatives.

Homing instinct

For Humboldt penguins, which nest on Peruvian cliffs and spend long periods foraging at sea, odour acts as an identifier when they return to colonies crowded with thousands of birds nesting in cracks and crevices.

"It's important for birds that live in large groups in the wild, like penguins, to know who their neighbours are so that they can find their nesting areas and also, through experience, know how to get along with the birds nearby," says animal behaviour expert Dr Jason Watters of the Chicago Zoological Society, which operates Brookfield Zoo.

"It could also be true that birds may be able to help zoo matchmakers in determining potential mates," says Watters.

"You could imagine that if (naturalists) were trying to reintroduce birds to an area, you could first treat the area with an odour the birds were familiar with. That would make them more likely to stay," he says.